1. Field of the Invention
The present invention relates to chemical assays, and more particularly to a system and method for infrared measurement of microbiological activity.
2. Discussion of Related Art
Biologists use indicator chemicals to enhance and accelerate the identification of microbial colonies when attempting to determine microbial concentration levels for specific samples being tested. One of the problems identified with using such indicator chemicals is that they can have a reaction to non-microbial stimuli such as treatment chemicals and drugs. This is particularly true for broad-spectrum microbial indicators such as TTC and other ORP indicator chemicals that are used in the enumeration of aerobic microbes present in a sample. This chemical positive reaction is particularly true of but not limited to microbial tests that use an aqueous testing matrix. The presence of reductive chemicals causes the TTC indicator to turn the normal end of test red hue whether microbes are present or not. This situation may lead to a false positive for microbes test result or an erroneous microbial concentration level determination. In some microbial testing applications, such as the culturing of urine samples, a false position may result from various types of antioxidant therapy (e.g., vitamin C and etc.) or certain types of antibiotics. The elimination of chemical positive results that are not biologically positive has a positive effect upon the microbial test analysis, as test results are not delayed by secondary tests. The occurrence of such chemical positive/biologic negative test results can vary greatly and in an unpredictable or known manner from one test application to another test application. Similar undesired test variation can occur from one sample to another sample with an application because of reasons of sample environment change. As an example for human urine testing a person providing a urine sample who is on antioxidant therapy can provide a chemically positive test sample which is not biologic positive in the morning period but provide a chemically negative and biologically negative in the afternoon. This occurs when the urine residuals of oxidant materials are high based upon the amount of antioxidant taken, time of dose and relative chemical health of the individual at the time of sampling. Similar difficulty can occur with samples taken from closed loop water-cooling systems. This result is particularly true for medical applications where the application of medicinal steps is made faster and fewer cases of antibiotic over dosing occur.
The enumeration and speciation of microbial populations may include the use various kinds of media plates, slants and or agar swabs. These analysis techniques do not yield, by themselves, the growth phase of a microbial population. Known techniques merely determine microbial presence, level and species. If the biologic analyst wishes to determine the growth phase of a microbial population at sampling time, a series of time consuming tests and calculations need to be performed with the specific intent of estimating the growth phase of the microbial population. Growth phase of microbial populations is an important factor in the proper analysis and control of many microbial populations.
Methods for speciation in samples having mixed microbe populations can be difficult. For example, in a mixed population, attempts to determine a particular species that may be the cause of an infection, e.g., a species having a highest concentration, are complicated by detection techniques. To determine the species in the sample, the sample is plated and grown on a media. Thus, all species in the sample are provided the opportunity for growth. Therefore, it can be difficult to determine a culprit of the infection.
Therefore, a need exists for a system and method of reducing chemical false positive results and determining microbial growth phase (log vs. lag) of detected microbial populations.